# JavaScript Exercises: Update the value of a node at a specific index in a Doubly Linked list

## JavaScript Data Structures: Exercise-17 with Solution

Write a JavaScript program that updates the value of a node at a specific index in a Doubly Linked list.

Sample Solution:

JavaScript Code:

``````class Node {
// Constructor function for creating a new node with a given value
constructor(value) {
this.value = value; // Assign the given value to the node
this.next = null; // Initialize the pointer to the next node as null
this.previous = null; // Initialize the pointer to the previous node as null
}
}
// Constructor function for creating a new doubly linked list with a head node having the given value
constructor(value) {
// Initialize the head node with the given value and no next or previous node
value: value, // Store the value of the head node
next: null, // Pointer to the next node in the list, initially set to null
previous: null // Pointer to the previous node in the list, initially set to null
};
this.length = 0; // Initialize the length of the list to 0
this.tail = this.head; // Set the tail node to the head node initially
}
if (this.head === null) { // If the list is empty
this.head = newNode; // Set the new node as both head and tail
this.tail = newNode;
}
else
{
newNode.previous = this.tail; // Set the previous pointer of the new node to the current tail node
this.tail.next = newNode; // Set the next pointer of the current tail node to the new node
this.tail = newNode; // Update the tail node to the new node
}
this.length++; // Increment the length of the list
}
update_Node(index, newValue) {
if (index < 0 || index > this.length) { // If the index is out of bounds
return false; // Return false indicating failure
}
for (let i = 0; i < index; i++) { // Iterate until reaching the node at the specified index
currentNode = currentNode.next; // Move to the next node
}
currentNode.value = newValue; // Update the value of the node at the specified index
return true; // Return true indicating success
}
printList(){
let current = this.head; // Start from the head of the list
let result = []; // Array to store the values of the nodes
while (current !== null) { // Iterate through the list until reaching the end
result.push(current.value); // Push the value of the current node to the array
current = current.next; // Move to the next node
}
console.log(result.join(' ')); // Log the values of the nodes separated by space
return this; // Return the DoublyLinkedList object for chaining
}
}
let numList = new DoublyLinkedList(); // Create a new instance of the DoublyLinkedList class
console.log("Original Doubly Linked Lists:"); // Print the original list
numList.printList();
console.log("Update Node value: Index = 2, Value = 33"); // Update the value of node at index 2
numList.update_Node(2,33);
numList.printList();
console.log("Update Node value: Index = 6, Value = 88"); // Update the value of node at index 6
numList.update_Node(6,88);
numList.printList();
console.log("Update Node value: Index = 1, Value = 55"); // Update the value of node at index 1
numList.update_Node(1,55);
numList.printList();
```
```

Output:

```Original Doubly Linked Lists:
2 3 4 5 6 7
Update Node value: Index = 2, Value = 33
2 33 4 5 6 7
Update Node value: Index = 6, Value = 88
2 33 4 5 6 88
Update Node value: Index = 1, Value = 55
55 33 4 5 6 88
```

Flowchart:

Live Demo:

See the Pen javascript-doubly-linked-list-exercise-17 by w3resource (@w3resource) on CodePen.

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